LA1787M. Functions FM front end FM IF Noise canceller Multiple AM up-conversion FM/AM switch MRC

Transcription

1 Ordering number : ENN6655 LA1787M Monolithic Linear IC Single-Chip Tuner IC for Car Radios Overview The LA1787M integrates all six blocks required in a car radio tuner on a single chip. Functions FM front end FM IF Noise canceller Multiple AM up-conversion FM/AM switch MRC Features Improved noise reduction methods The FM front end provides excellent -signal characteristics equivalent to those of the LA119M. Superlative listenability due to improved medium and weak field noise canceller characteristics. Improved separation characteristics Anti-birdie filter Improved AM and FM thermal characteristics Excellent FM signal meter linearity Modified N.C. circuit for improved noise rejection Improved AM adjacent channel interference characteristics ( 0 khz) Double conversion AM tuner (up conversion) Reduces the number of external components required as compared to earlier double conversion tuners, in particular, no crystal is required (when used in conjunction with the LC71). Sample-to-sample variation reduction circuit built into the FM IF circuit. (Fixed resistors are used for the SD, keyed AGC, mute on adjustment, ATT, SNC, and HCC functions.) Improved FM separation temperature characteristics The LA1787 inherits the block arrangement of the LA1780M and supports pin-compatible designs. Package Dimensions unit : mm (typ) QIP6E(1X1) max Allowable power dissipation, Pd max mw Mounted on a 0 x 80 x 1. mm glass epoxy printed circuit board Independent IC Ambient temperature, Ta C Semiconductor Components Industries, LLC, 011 January, RM (OT) No /5

2 Specifications Maximum Ratings at Ta = 5 C Operating Conditions at Ta = 5 C LA1787M Parameter Symbol Conditions Ratings Unit 1 max Pins 6, 0, and 61 9 V Maximum supply voltage max Pins 7, 5, 5, 59, and 60 1 V Allowable power dissipation Pd max Ta 55 C 950 mw Operating temperature Topr 0 to 85 C Storage temperature Tstg 0 to 150 C Parameter Symbol Conditions Ratings Unit Pins 6, 7, 0, 5, 5, 59, 60, and 61 8 V Recommended supply voltage ST IND Pin 6 5 V Operating supply voltage range op 7.5 to 9.0 V Operating Characteristics at Ta = 5 C, = 8.0V, in the specified test cricuit for the FM IF input Ratings Parameter Symbol Conditions min typ max unit [FM Characteristics] At the FM IF input Current drain I CCO -FM No input, I0 I5 I5 I59 I60 I ma Demodulation output V O -FM 10.7 MHz, 100dBµ, 1 khz, 100%mod, The pin 15 output mvrms Pin 1 demodulation output V O -FM MHz, 100dBµ, 1 khz, 100%mod, The pin 1 output mvrms Channel balance CB The ratio between pins 15 and 16 at 10.7 MHz, 100 dbµ, 1 khz db Total harmonic distortion THD-FM mono 10.7 MHz, 100 dbµ, 1 khz, 100% mod, pin % Signal-to-noise ratio: IF S/N-FM IF 10.7 MHz, 100 dbµ, 1 khz, 100% mod, pin db AM suppression ratio: IF AMR IF 10.7 MHz, 100 dbµ, 1 khz, f m = 1 khz, 0% AM, pin db Att MHz, 100 dbµ, 1 khz. The pin 15 attenuation when V goes from 0 to V db Muting attenuation Att MHz, 100 dbµ, 1 khz. The pin 15 attenuation when V goes from 0 to V* db Att MHz, 100 dbµ, 1 khz. The pin 15 attenuation when V goes from 0 to V * 8 8 db Separation Separation 10.7 MHz, 100 dbµ, LR = 90%, pilot = 10%. The pin 15 output ratio 0 0 db Stereo on level ST-ON The pilot modulation such that V6 < 0.5 V 1... % Stereo off level ST-OFF The pilot modulation such that V6 >.5 V % Main total harmonic distortion THD-Main L 10.7 MHz, 100 dbµ, LR = 90%, pilot = 10%. The pin 15 signal % Pilot cancellation PCAN 10.7 MHz, 100 dbµ, pilot = 10%. The pin 15 signal/the pilot level leakage. DIN audio 0 0 db SNC output attenuation AttSNC 10.7 MHz, 100 dbµ, L-R = 90%, pilot = 10%. V8 = V 0.6 V, pin db 10.7 MHz, 100 dbµ, 10 khz, LR = 90%, pilot = 10%. AttHCC-1 V9 = V 0.6 V, pin 15 HCC output attenuation db AttHCC MHz, 100 dbµ, 10 khz, LR = 90%, pilot = 10%. V9 = V 0.1 V, pin db Input limiting voltage Vi-lim 100 dbµ, 10.7 MHz, 0% modulation. The IF input such that the input reference output goes down by db 0 7 dbµ Muting sensitivity Vi-mute The IF input level (unmodulated) when V = V 7 5 dbµ SD-sen1 FM The IF input level (unmodulated) (over 100 mv rms) SD sensitivity such that the IF counter buffer output goes on dbµ SD-sen FM dbµ IF counter buffer output V IFBUFF-FM 10.7 MHz, 100 dbµ, unmodulated. The pin output mvrms V SM FM-1 No input. The pin DC output, unmodulated V Signal meter output V SM FM- 50 dbµ. The pin DC output, unmodulated V V SM FM- 70 dbµ. The pin DC output, unmodulated V V SM FM- 100 dbµ. The pin DC output, unmodulated V Muting bandwidth BW-mute 100 dbµ. The bandwidth when V = V, unmodulated khz Mute drive output V MUTE dbµ, 0 dbµ. The pin DC output, unmodulated V Continued on next page. No /5

3 Continued from preceding page. Ratings Parameter Symbol Conditions min typ max unit [FM FE Mixer Input N-AGC on input V N -AGC 8 MHz, unmodulated. The input such that the pin voltage is.0 V or below dbµ W-AGC on input V W AGC 8 MHz, unmodulated. The input such that the pin voltage is.0 V or below. (When the keyed AGC is set to.0 V.) dbµ Conversion gain A.V 8 MHz, 80 dbµ, unmodulated. The FE CF output mvrms Oscillator buffer output V OSCBUFFFM No input mvrms [NC Block] NC input (pin 0) Gate time τgate1 f = 1 khz, for a 1-µs, 100-mV p-o pulse 55 µs Noise sensitivity SN The level of a 1 = khz, 1-µs pulse input that starts noise canceller operation. Measured at pin 0. 0 mvp-o The pulse rejection effect provided by the noise canceller. NC effect SN-NC For a repeated 1-µs wide pulse, frequency = 10 khz, 150 mv p-o. The ratio of the FM mode pin 15 output 5 referenced to the AM mode pin 15 output (effective value) [Multipath Rejection Circuit] MRC input (pin 7) MRC output VMRC V = 5 V... V MRC operating level MRC-ON The pin input level at f = 70 khz such that pin goes to 5 V and pin 7 goes to V mvrms [AM Characteristics] AM ANT input Practical sensitivity S/N-0 1 MHz, 0 dbµ, f m = 1 khz, 0% modulation, pin 15 0 db Detector output V O -AM 1 MHz, 7 dbµ, f m = 1 khz, 0% modulation, pin mvrms Pin 1 detector output V O -AM1 1 MHz, 7 dbµ, f m = 1 khz, 0% modulation, pin mvms 1 MHz, 7 dbµ, referenced to the output, the input amplitude AGC F.O.M. V AGC-FOM such that the output falls by 10 db. Pin db Signal-to-noise ratio S/N-AM 1 MHz, 7 dbµ, f m = 1 khz, 0% modulation 7 5 db Total harmonic distortion THD-AM 1 MHz, 7 dbµ, f m = 1 khz, 80% modulation 0. 1 % V SM AM-1 No input V Signal meter output V SM AM- 1 MHz, 10 dbµ, unmodulated V Oscillator buffer output V OSCBUFF AM1 No input, the pin 15 output mvrms Wide band AGC sensitivity W-AGCsen1 1. MHz, the input when V6 = 0.7 V dbµ W-AGCsen 1. MHz, the input when V6 = 0.7 V (seek mode) dbµ SD sensitivity SD-sen1 AM 1 MHz, the ANT input level such that the IF counter output turns on. 0 6 dbµ SD-sen AM 1 MHz, the ANT input level such that the SD pin goes to the on state. 0 6 dbµ IF buffer output V IFBUFF-AM 1 MHz, 7 dbµ, unmodulated. The pin output mvrms Note: These measurements must be made using the either the IC or KS877 IC socket (manufactured by Yamaichi Electronics). * 1. When the resistor between pin 58 and ground is 00 kω. *. When the resistor between pin 58 and ground is 0 kω. No /5

4 Function List FM Front End (Equivalent to the Sanyo LA119) Double input type double balanced mixer Pin diode drive AGC output MOSFET second gate drive AGC output Keyed AGC adjustment pin Differential IF amplifier Wide band AGC sensitivity setting pin, and narrow band AGC sensitivity setting pin Local oscillator FM IF IF limiter amplifier S-meter output (also used for AM) 6-stage pickup Multipath detection pin (shared FM signal meter) Quadrature detection AF preamplifier AGC output Band muting Weak input muting Soft muting adjustment pin Muting attenuation adjustment pin IF counter buffer output (also used for AM) SD (IF counter buffer on level) adjustment pin SD output (active high) (also used for AM) Noise Canceller High-pass filter (first order) Delay circuit based low-pass filter (fourth order) Noise AGC Pilot signal compensation circuit Noise sensitivity setting pin Function for disabling the noise canceller in AM mode Multiplex Functions Adjustment-free VCO circuit Level follower type pilot canceller circuit HCC (high cut control) Automatic stereo/mono switching VCO oscillation stop function (AM mode) Forced monaural SNC (stereo noise controller) Stereo display pin Anti-birdie filter AM Double balanced mixer (1st, nd) IF amplifier Detection RF AGC (narrow/wide) Pin diode drive pin IF AGC Signal meter output (also used for FM) Local oscillator circuits (first and second) Local oscillator buffer output IF counter buffer output (also used by the FM IF) SD (IF counter buffer on level) adjustment pin SD output (active high) (also used for AM) Wide AGC Detection output frequency characteristics adjustment pin (low cut, high deemphasis) AM stereo buffer MRC (multipath noise rejection circuit) AM/FM switching output (linked to the FM ) No /5

5 Operating Characteristics and Symbols Used in the Test Circuit Diagrams Switches (SW) Switch on = 1, SW off = 0 There are two switches that use signal transfer. SW: switches between the mixer input and the IF input. SW: switches between noise canceler input and IF output noise canceler input. Types of SG used PG1 (AC1) AC AC AC AC5 Used for noise canceler testing. A pulse generator and an AF oscillator are required. Used for FM front end testing. Outputs an 8 MHz signal. Used for FM IF, noise canceler, and MPX testing. Outputs a 10.7 MHz signal. Stereo modulation must be possible. Used for AM testing. Outputs 1 MHz and 1. MHz signals. Used with the MRC. Can also be used for AF and OSC. Power supply 8 V 1 5 V SD, stereo, seek/stop 0.1 V / 0.7 V / V / V These levels Keyed AGC, Mute ATT 0.1 V / 0.6 V / V must be variable. HCC, SNC, SASC (MRC) Switches Parameter ON OFF SW1 AM/FM switching. The FE is supplied to pin 6. FM AM SW FM IF switching. Pin 51/FE output FE IF OUT (A) AC (B) SW For conversion gain testing Conversion gain measurement (A) Other/purposes SW For switching between noise canceler input and IF output noise canceler. AC1 (A) Other/purposes SW5 High-speed SD High-speed SD Other/purposes SW6 SEEK/STOP (IF BUFF ON/OFF) STOP Seek (IF buffer output) SW7 MUTE ATT 00 kω MUTE 00 kω OFF SW8 MUTE ATT 0 kω MUTE 0 kω OFF SW9 For pilot cancellation testing When pilot cancellation is used When pilot cancellation is not used SW10 Mute off (pin ) MUTE OFF MUTE ON Trimmers (variable resistors) VR1 VR Separation adjustment Pilot cancellation adjustment Test Points DC voltages VD1 FM RF AGC voltage Pin VD AM/FM SD, AM Tweet, FM stereo indicator Pin 6 VD AM/FM S-meter Pin VD MRC output Pin 7 VD5 Mute drive output Pin VD6 AM antenna damping voltage Pin 6 VD7 N.C. Gate time Pin 8 AC voltages VA1 AM/FM OSC Buff Pin VA First IF output Pin 5 CF pin 51 load level (10.7 MHz) VA IF counter buffer Pin (10.7 MHz/50 khz) VA MPX OUT Left ch Pin 15 (AF) VA5 MPX OUT Right ch Pin 16 (AF) No /5

6 Pin Descriptions Pin No. Function Description Equivalent circuit ANT 6 pin RF AGC An antenna damping current flows 1 Antenna damping drive when the RF AGC voltage (pin ) reaches V D. 1000pF 100Ω 1 00Ω 1000pF 100Ω A1555 RF AGC Used to control the FET second gate. FET nd GATE 1kΩ ANT DAMPING DRIVER N AGC DET W AGC DET KEYED AGC A1556 F.E.GND OSC Oscillator connection 5pF VT 0pF kω A VCC 7 AM OSC AM first oscillator This circuit can oscillator up to the SW band. An ALC circuit is included. A L C A1558 Continued on next page. No /5

7 Continued from preceding page. Pin No. Function Description Equivalent circuit kω kω 15kΩ After setting up the medium field (about 50 dbµ) sensitivity with the 8 Noise AGC sensitivity noise sensitivity setting pin (pin 8), 9 AGC adjustment set the weak field (about 0 to 0 dbµ) sensitivity with the AGC adjustment pin (pin 9) 00Ω 8 9 kω 0.01µF 1MΩ 0.7µF A µF 6800pF.9kΩ Recording circuit used during Memory circuit connection 1 noise canceller operation. Differential amp Gate circuit LPF A1560 0kΩ 1 Pilot input Pin 1 is the PLL circuit input pin. PLL N.C µF A N.C, MPX, MRC, GND Ground for the N.C., MPX, and MRC circuits. Continued on next page. No /5

8 Continued from preceding page. Pin No. Function Description Equivalent circuit 15 MPX output (left) 16 MPX output (right) Deemphasis 50 µs: µf 75 µs: 0.0 µf.kω.kω µF 0.015µF A156 Adjustment is required since the pilot signal level varies with the 17 Pilot canceller signal output sample-to-sample variations in the IF output level and other parameters. 0kΩ 6.7kΩ µF 100kΩ A Pilot canceller signal output Pin 18 is the output pin for the pilot canceller signal. 1.5kΩ µF 100kΩ A156 Continued on next page. No /5

9 LA1787M Continued from preceding page. Pin No. Function Description Equivalent circuit Composite signal 5kΩ DECODER 19 Separation adjustment pin Use a trimmer to adjust the subdecoder input level. (The output level is not modified in mono and main modes.) kω 19 0kΩ 0.07µF A1565 V REF CSB 91 JF VCO The oscillator frequency is 91 Hz. KBR-91F108 (Kyocera Corporation) CSB-91JF108 (Murata Mfg. Co., Ltd.) 10pF A1566 V REF 1 PHASE COMP. PHASE COMP. 15kΩ 15kΩ 19kΩ 1 A1567 Continued on next page. No /5

10 LA1787M Continued from preceding page. Pin No. Function Description Equivalent circuit This pin functions both as the IF counter buffer (AC output) and as the seek/stop switch pin. The voltage V switches between the following three modes. IF counter buffer seek/stop During FM reception: switching 5 V: Seek mode.5 V: Forced SD mode 0 V: Reception mode AM reception (two modes: 0 and 5 V) 5 V: Seek mode 0 V: Reception mode SD SW.9V 50kΩ IF BUFF. 150Ω 1.V 51kΩ STOP 50F AM MUTE IF counter buffer Forced SEEK SD:.5V 5V A1568 AM/FM signal meter Fixed-current drive signal meter output In AM mode, pin outputs a Dedicated FM signal meter 1-mA current. Thus the HCC circuit is turned off. FM S-meter AM S-meter AM/FM SW Outputs a 1-mA current during AM reception MRC AM/FM SW A Stereo indicator for the SD pin The voltage V switches between three modes as follows. FM reception: 5 V: The SD pin operates linked to the IF counter buffer..5 V: Forced SD mode: operates as the SD pin. 0.7 V: Reception mode: stereo indicator AM reception: (two modes: 0 and 5 V) 5 V: Operates as the seek SD pin. 0 V: Reception mode. Not used. 6 AM/FM SD 100kΩ Seek/stop switching Stereo indicator VDD A1570 Continued on next page. No /5

11 LA1787M Continued from preceding page. Pin No. Function Description Equivalent circuit µa C 7 MRC control voltage time constant The MRC detector time constant is determined by a 100 Ω resistor and C when discharging and by the -µa current and C when charging. 100Ω 7 Pin 8 A1571 V REF 8 SNC control input The sub-output is controlled by a 0 to 1-V input. 8 A157 V REF The high band frequency output is controlled by a 0 to 1-V input. It can also be controlled by the 9 HCC control input MRC output. Use a resistor of at least 100 kω when controlling with the pin FM S-meter signal. 1µF 9 A157 Continued on next page. No /5

12 Continued from preceding page. Pin No. Function Description Equivalent circuit FM detector output 1 0 Noise canceller input Pin 0 is the noise canceller input. The input impedance is 50 kω. Pin 1 is the AM and FM detector output In FM mode, this is a lowimpedance output. 1 AM/FM detector output In AM mode, the output impedance is 10 kω. To improve the low band separation, use a coupling capacitor of over 10 µf. AM detector Noise canceller 0 1µF 50kΩ.V A157 IF S-meter output and MRC DC input FM S-meter output block MRC AC input block Adjust the external 1-kΩ resistor to attenuate the MRC AC input and control the circuit. 1µF 1kΩ MRC input A1575 C1 The muting time constant is determined by an external RC circuit as described below. Attack time: T A = 10 kω C1 Release time: T R = 50 kω C1 Noise convergence adjustment Mute drive output The noise convergence can be adjusted when there is no input signal by inserting a resistor between pin and ground. Muting off function Ground pin through a -kω resistor. SEEK OFF SOFT MUTE HOLE DET VCC Band muting 0.1µF 50kΩ 50kΩ MUTE AMP. SD circuit A1576 Continued on next page. No /5

13 LA1787M Continued from preceding page. Pin No. Function Description Equivalent circuit 0.1µF VREF R1 C The resistor R 1 determines the width of the band muting function. Increasing the value of R 1 narrows the band. Reducing the value of R 1 widens the band. AGC 5 QD output Null voltage 6 QD input When tuned, the voltage between 7 V REF pins and 7, V 7, will be 0 V. The band muting function turns on when V V. HOLE DET R Quadrature detector pf 90Ω V 7 =.9 V 1kΩ IF limitter amplifier Band muting A1577 R SD ADJ 8 8 FM SD ADJ A 10-µA current flows from pin 8 and, in conjunction with the external resistance R, determines the comparison voltage. 10µA SD Comparator S-meter A1578 S-meter 6.kΩ The keyed AGC operates when the voltage created by dividing the pin S-meter output voltage by the 6. and.6 kω resistors 9 Keyed AGC becomes lower than the voltage AM stereo buffer determined by the resistor between pin 9 and ground. KEYED AGC Comparator 1.V VCC.6kΩ 90µA 9 This pin also is used as the AM stereo IF buffer pin. AM IF out 50pF 150Ω A1579 Continued on next page. No /5

14 LA1787M Continued from preceding page. Pin No. Function Description Equivalent circuit 0kΩ 0kΩ The HCC frequency characteristics 1 HCC capacitor are determined by the external capacitor connected at this pin. 1 00pF A1580 This pin is used to change the frequency characteristics of the unneeded audio band under 100 Hz in AM mode to produce a clear audio signal. C Note: The LC capacitor must be connected between this pin and (pin 0). AM L.C. pin This is because the detector circuit operates referenced to. DET 50kΩ 1kΩ The cutoff frequency f C is determined by the following formula. 50kΩ 1kΩ f C = 1/π 50 kω C A kHz 0 BIAS 0kΩ Inserting a 1-MΩ resistor between Pilot detector pin and will force the IC to mono mode. 0kΩ 0kΩ 1µF A158 Continued on next page. No /5

15 Continued from preceding page. Pin No. Function Description Equivalent circuit 0.0µF 0kΩ C.µF IF AGC G1; Used for time constant switching during seeks. Reception τ =. µf 00 kω Seek τ =. µf 10 Ω The external capacitors are connected to. This is because the IF amplifier operates referenced to. DET G1 50kΩ 50kΩ IF AGC SEEK ON 10Ω A158 Pin 0 5 Pin 0 5 IF output The IF amplifier load DET A158 50pF 6 100Ω AM antenna damping I6 = 6 ma (maximum) 6 drive output This is the antenna damping Wide band AGC input current. 0kΩ VCC W.AGC AMP. ANT DAMPING DRIVER A1585 Continued on next page. No /5

16 Continued from preceding page. Pin No. Function Description Equivalent circuit 0kΩ 7 R 7 FM muting on level adjustment Modify the value of the external resistor to adjust the muting on level. 10µA Pin Inverter MUTE A V RF AGC rectification capacitor The low frequency distortion is determined as follows: Increasing C8 and C57 improves 8 RF AGC bypass the distortion but makes the 57 RF AGC response slower..µf 8 Antenna damping Reducing C8 and C57 aggravates the distortion but makes the response faster. For AGC use 57 7µF A1587.6V 50 IF bypass 51 FM IF input Due to the high gain of the limiter amplifer, care must be taken when choosing the grounding point for the limiter amplifer input capacitor to prevent oscillation. 0.0µF 50 0Ω 51 IF in A1588 kω 100Ω 5 IF input The input impedance is kω. 5 A1589 Continued on next page. No /5

17 LA1787M Continued from preceding page. Pin No. Function Description Equivalent circuit Input and output pin or the first IF amplifier Inverting amplifier 5 IF amplifier output V56 = V 56 IF amplifier input Input impedance: R IN = 0 Ω IF OUT 5.75V 00Ω 00Ω V5 = 5. V Output impedance R OUT = 0 Ω IF IN 56 A1590 Pin 0 Pin Mixer output: 10 µa 9 Mixer input The mixer coil connected to the pin 5 mixer output must be wired to (pin 0). The pin 9 mixer input impedance is 0 Ω 9 OSC 0Ω A pin W-AGC N-AGC Pins 55 and 58 include built-in DC cut capacitors. The AGC on level is determined by the values of the capacitors C1 and C. 55 W-AGC IN Pin 55 functions as the SD AM SD ADJ sensitivity adjustment pin in AM mode. 58 N-AGC IN Muting attenuation The output current I55 is 50 µa, adjustment pin and V55 varies depending on the value of the external resistor. The SD function operates by comparing V55 with the S-meter voltage. MIX IN C1 C pF 50µA 50pF MIX OUT AM SD Signal meter A159 Continued on next page. No /5

18 LA1787M Continued from preceding page. Pin No. Function Description Equivalent circuit 1ST.IF O S C Mixer output Mixer input Double balanced mixer Pins 59 and 60 are the mixer 10.7-MHz output Pins 6 and 6 are the mixer input. This is an emitter insertion type circuit, and the amount of insertion is determined by the capacitors C1 and C. Note:The lines for pins 6 and 6 must be kept separated from the lines for pins 59 and 60. RF AMP 0Ω C1 5pF C 5pF Ω 60Ω A159 6 Front end AM/FM switching Pin 6 functions both as the FM front end and the AM/FM switching circuit. V6 voltage Mode When 8 V FM SD 8V 6 FM.F.E AGC 510Ω 100kΩ.V AM/FM switching circuit OPEN AM GND A159 AM 1st MIX to RF Amp st MIX INPUT First mixer input The input impedance is about 10 kω..1v A1595 Crystal oscillator circuit 10 AM nd OSC The Kinseki, Ltd. HC-9/U-S and a C L of 0 pf must be used. 5.6V 0pF pf 10 to nd MIX X tal A1596 No /5

19 Block Diagram CHCC 00pF kΩ µF µF OSC 18pF 1 ANT D BUFF AM 1ST OSC AMP NOISE AMP PICAN INPUT AGC TRIG GATE COUNTER HPF ANT D OSC BUFF OSC BUFF IF limiter amplifier Q.DET MUTE AMP 800pF DET L.C. IF AGC AMVSM AM SD IF BUFF FMVSM FM SD HOLE DET DC-C DET MRC MUTE DRIVE AFC CLAMP MIX RF AGC WB AGC W.B.AGC TWEET AM FM VREF SEEK SW SD/ST IND IF REG AM/FM SW VCO STOP SNC HCC MAIN HC RF AGC KEYED AMP AGC INPUT FF 19k<90k FF 19k<0 PHASE COMP VCO AM/FM MIX BUFF 0kΩ LPF FF 8k<0 FF PILOT DET SUB DEC TRIG P-CAN MAT RIX 00pF 0kΩ FE GND RF AGC kω 18pF 6800pF 0.01µF ANT D 1µF AM LEVEL ADJ AM HC HCC SNC 1µF 1µF 5.6kΩ 0.7µF 0.µF 1µF 0.07µF 0kΩ SEP.ADJ 100kΩ 0.01µF PI.CAN ADJ 1µF 100kΩ AM OSC 10.6MHz 0.7µF 1MΩ 0.01µF 0.0µF 0.0µF 0.0µF 1kΩ 100kΩ 50kΩ 5pF 10pF AM/FM OSC BUFF 5pF 0pF 1µF GND AM/FM S-METER MPX OUT CSB91JF108 GND 5V N.C.MPX GND NC MPX GND FM METER DET OUT NC-IN MUTE DRIVE 0.7µF AFC IN 0.7µF QD OUT QD IN VREF FM SD ADJ. 0kΩ KEYED AGC 6.8kΩ 0.µF 100µF 0kΩ 0.1µF AM LC 0.0µF PILOT DET 1µF.µF IF7 11kΩ RFAGC GND.µF VCC 0.0µF 100µH 0MH 0.0µF 100µH 15pF ANTD 0.0µF 15pF 15pF 7µF 100kΩ 0.0µF 0Ω 1kΩ 5 0kΩ 6pF 0Ω 1MH FC18 FM IF IN 0Ω 100Ω FM IF OUT AM IF IN AM SD ADJ AM MIX OUT FM WB AGCIN FE IF IN MUTE ATT 8pF FE 0.0µF 5pF 5pF 0.0µF FMIF AM GND FMIF AM NC MPX FM/AM VSM RIGHT CH. LEFT CH. 18pF 0kΩ 100kΩ 0Ω 0Ω 100Ω 0.0µF 00kΩ GND 0.0µF SK6 1000pF 180Ω FM GND GND 0.1µF 0kΩ 100kΩ 9pF 1000pF 1000pF 100F 100kΩ 0.0µF 9pF FM ANT IN 100kΩ AM RF GND 1000pF pf pf TO AM STEREO (IF OUT) SEEK AM/FM SD STOP FM ST IND. FM/AM VT AM ANT IN AM 0.0µF.kΩ 100kΩ 100kΩ SK µF 1µF pf pf 51kΩ 100pF 100pF 100pF 100pF 7.MHz 0.µF 10µF 0.µF kω kω 0kΩ kω kω 0kΩ 51kΩ.kΩ.7kΩ 68pF 00kΩ 1kΩ 1.5kΩ kω 100kΩ 1kΩ 100µF kω 100kΩ 100µF 1kΩ 100pF R ON SD/MONO ST MUTE ADC RDS LC86718 DO CL CI CE 10µF 10µF 10µF 10µF 5.6V 9.1V R L B 1V 11 FM/AM AM IN LC716M 16 FM IN DO 17 V DD CL 18 PD CI 19 V SS CE A1597 No /5

20 AC Characteristics Test Circuit 8V GND 0.7µF FM SD ADJ. KEYED AGC AM LC PILOT DET.kΩ VD5 0.1µF VREF 6.8kΩ kω 0.µF 100µF 00pF 0.0µF 1µF.µF MUTE OR ADJ 180kΩ.µF IF OUT IF IN SW B IF7 15kΩ MUTE DRIVE AFC IN QD OUT A SW ( i ) MIX QD IN 0.1µF CHCC 0kΩ VCC MRC-IN RFAGC µF FM S-METER OSC BUFF OSC ANT D 9 ADJ AM LEVEL DET OUT 1 MUTE AMP 50 FM IF IN 18pF SW (T) B A AM HC 800pF 1µF Q.DET NC-IN 0Ω 00Ω PG1 (AC1) 0 51 NC-IN BUFF 0.0µF HCC 9 MUTE DRIVE HOLE DET FMVSM FM SD AMVSM AM SD IF AGC DET 5 AM IF IN SNC L.C. 8 AFC CIAMP DC-C DET 100kΩ 5 1µF IF BUFF FM IF OUT 7 5 VD MIX VD 6 MRC RF AGC W.B. AGC TWEET 55 AM SD ADJ AM MIX OUT FM WB AGCIN 100kΩ GND FE IF IN kΩ 0.7µF 50kΩ AM/FM S-METER FF 19<90 PHASE COMP 57 k SNC VA HCC LPF HPF AM FM VREF 10pF 0Ω 58 FM/AM IFBUFF. 5.6kΩ VCO FF 19<0 W.B.AGC RF AGC 59 50kΩ 0.µF VCO STOP FM/AM SW KEYED AGC FF REG MUTE ATT 1µF CSB91JF TRIG PILOT DET SW5 MIX 0 BUFF FE 0Ω 61 P-CAN 19 FF 8k<0 BUFF AM 1ST OSC AM/FM 0kΩ 0.07µF 6 8V 0.0µF VR1 0kΩ pf SW9 SEP. ADJ 18 FF MAIN HC pf 6 100kΩ MA TRIX SUB DEC AGC TRIG GATE 5pF 1MΩ 9pF VR 0.01µF PI.CAN ADJ 17 ANT 6 D 5pF 100kΩ OSC AM MPX 0pF OSC OUT 6800pF 0.01µF 5pF FE GND RF AGC ANT D 0.015µF 0.015µF N.C.MPX GND 0.7µF 0.01µF 1MΩ 100Ω 5pF 00pF 0.0µF 10.6MHz X TAL 0kΩ 0pF 1µF GND 100Ω 0.0µF RIGHT CH. LEFT CH. VCC SW1 10µF 0.0µF 8V VA6 VA1 VA9 AM/FM OSC BUFF VT FM FM GND 0.0µF VA 50Ω 00Ω 0Ω 0.0µF 1mH 1.6kΩ 100µH FC18 100µH 6.8mH 0.0µF 100kΩ 7µF 0.0µF 510Ω ANTD 0.0µF 0kΩ SW8 SW7 5Ω 50Ω 1000µF 50Ω 50Ω 0Ω 15pF 65pF JIS DUMMY VD6 5V VCC1 AC5 IF limiter amplifier HCC SNC VCC 100kΩ SEEK AM/FM SD STOP AM ST BUFFER FM ST IND. SW6 VD VCC VA8 8V 0.0µF pf SW10 0kΩ VCC 50Ω AC SG 00kΩ 0.0µF AC1 SG1 VD1 AC SG A1598 1MΩ 10µF VA7 No /5

21 Test Conditions Switch states Parameter Symbol SW1 SW SW SW SW5 SW6 SW7 SW8 SW9 SW10 Current drain I CCO -FM ON b OFF b ON OFF OFF ON Demodulation output V O -FM ON b OFF b ON OFF OFF ON Pin 1 demodulation output V O -FM1 ON b OFF b ON OFF OFF ON Channel balance CB ON b OFF b ON OFF OFF ON Total harmonic distortion (FM) THD-FMmono ON b OFF b ON OFF OFF ON Signal-to-noise ratio: IF S/N-FM IF ON b OFF b ON OFF OFF ON AM suppression ratio: IF AMR IF ON b OFF b ON OFF OFF ON Att-1 ON b OFF b ON OFF OFF ON Muting attenuation Att- ON b OFF b ON OFF OFF ON Att- ON b OFF b ON OFF OFF ON Separation Separation ON b OFF b ON OFF OFF ON Stereo on level ST-ON ON b OFF b ON OFF OFF ON Stereo off level ST-OFF ON b OFF b ON OFF OFF ON Main total harmonic distortion THD-Main L ON b OFF b ON OFF OFF ON Pilot cancellation PCAN ON b OFF b ON OFF OFF OFF/ON SNC output attenuation AttSNC ON b OFF b ON OFF OFF ON HCC output attenuation 1 AttHCC-1 ON b OFF b ON OFF OFF ON HCC output attenuation AttHCC- ON b OFF b ON OFF OFF ON Input limiting voltage Vi-lim ON b OFF b ON OFF OFF ON ON Muting sensitivity Vi-mute ON b OFF b ON OFF OFF ON SD sensitivity 1 SD-sen1 FM ON b OFF b OFF OFF OFF OFF ON SD sensitivity SD-sen FM ON b OFF b ON OFF OFF OFF ON IF counter buffer output V IFBUFF-FM ON b OFF b OFF OFF OFF OFF ON V SM FM-1 ON b OFF b ON OFF OFF ON Signal meter output (FM) V SM FM- ON b OFF b ON OFF OFF ON V SM FM- ON b OFF b ON OFF OFF ON V SM FM- ON b OFF b ON OFF OFF ON Muting bandwidth BW-mute ON b OFF b ON OFF OFF ON Mute drive output V MUTE-100 ON b OFF b ON OFF OFF ON N-AGC on input V NAGC ON a ON b ON OFF OFF W-AGC on input V WAGC ON a ON b ON OFF OFF Conversion gain A.V ON a ON b ON OFF OFF Oscillator buffer output V OSCBUFFFM ON a ON b ON OFF OFF Gate time 1 τgate1 ON OFF a ON OFF OFF Noise sensitivity SN ON OFF a ON OFF OFF NC effect SN-NC ON/OFF OFF a ON OFF OFF MRC output V MRC ON OFF b ON OFF OFF MRC operating level MRC-ON ON OFF b ON OFF OFF Practical sensitivity S/N-0 OFF OFF b ON ON Detection output V O -AM OFF OFF b ON ON Pin 1 detection output V O -AM1 OFF OFF b ON ON AGC F.O.M. V AGC-FOM OFF OFF b ON ON Signal-to-noise ratio S/N-AM OFF OFF b ON ON Total harmonic distortion (AM) THD-AM OFF OFF b ON ON Signal meter output (AM) V SM AM-1 OFF OFF b ON ON V SM AM- OFF OFF b ON ON Oscillator buffer output V OSCBUFF AM-1 OFF OFF b ON ON Wide band AGC sensitivity W-AGCsen 1 OFF OFF b ON ON W-AGCsen OFF OFF b ON ON SD sensitivity SD-sen1 AM OFF OFF b OFF OFF SD-sen AM OFF OFF b OFF OFF IF buffer output V IFBUFF-AM OFF OFF b OFF OFF No /5

22 Usage Notes 1. Notes on and Ground Pin 0 for the FM IF, AM, NC, MPX, and MRC blocks Pin 5 Ground for the FM IF and AM blocks Pin 1 Ground for the NC, MPX, and MRC blocks Pin 61 for the FM front end, AM first mixer, and first oscillator blocks * Pin 6 for the FM front end and AGC blocks, and the AM/FM switching pin Pin Ground for the FM front end, first mixer, and first oscillator blocks *: When applying the voltage to pin 6, that voltage must not exceed the pin 0 and pin 61 voltages. (This condition must be checked carefully when first applying the pin 6 voltage.). Notes on AM Coil Connection The used for the first oscillator coil connected to pin 7 must be at the same potential as pin 61. Connect to the IFT connected with pin 5, and to the MIX coil connected with pin 5. must be at the same potential as pin 0.. AM/FM Switching Pin 6 is also used as the FM front end and RF AGC Pin 6 voltage Mode 8 FM OPEN AM Fig. 1 LA1787M Overview 1. Notes on the LA1781M, LA178M, and LA1787M The LA178M is a version of the LA1781M that uses an external oscillator circuit, and has the same characteristics as the LA1781M. The LA1787M is a version of the LA178M that features improved characteristics. LA1781M LA178M LA1787M This product is a version of the LA1781M with the oscillator circuit removed. It supports the use of an external oscillator circuit. It has the same characteristics as the LA1781M. The LA1787M features improved characteristics over the LA1781M and LA178M. No /5

23 . Modified circuits The following characteristics have been improved over those of the The LA178M. The AM adjacent channel interference characteristics ( 0 khz) have been improved. The AM S-meter curve slope has been increased. The FM separation temperature characteristics have been improved. The stereo indicator sensitivity has been improved. The FM oscillator circuit has been omitted. (1) AM interference characteristics improvement The second signal interference and suppression have been improved for adjacent channels (±0 khz) by increasing the AM second mixer input dynamic range. () The AM S-meter curve slope has been increased. The slope of the AM S-Meter curve has been increased from that of the LA1781M and LA178M. 7 AM S-Meter Voltage 6 S-meter voltage V 5 LA1787M LA1781M LA1780M Antenna input dbµ () FM separation temperature characteristics improvement The temperature characteristics have been improved, the amount of change in the separation due to drift when at power on has been stabilized. This makes it easier to adjust the separation. 60 Change in Separation (LA1781M): First IF Input 60 Change in Separation (LA1787M): First IF Input Change in separation db Change in separation db Time after power on minutes Time after power on minutes No /5

24 () Stereo indicator sensitivity improvement The stereo indicator sensitivity (on/off) is equivalent to that of the LA1780M Stereo on level Stereo off level LA1781M/178M.1%.1% LA1787M/1780M.6% 1.6% (Typical value) *: The pilot level such that the stereo indicator goes on or off for a 10.7 MHz unmodulated IF input. (5) FM oscillator circuit removed The internal FM oscillator circuit provided in the LA1781M has been removed. The FM oscillator level can be adjusted by constructing an external circuit block. *: However, this requires more external parts than the LA1781M: 1 transistor and resistors/capacitors. IC internal IC internal Vt Vt A1600 A1601 LA1787M/178M FM OSC LA1780M/1781M FM OSC. Gain distribution The table below shows the gain distribution of the LA1780M, LA178M, and LA1787M. (These are measured values.) Compared to the LA178M, the total gain is lower. 1st MIX (10.7) 1st IF (10.7) nd MIX (50) nd IF (50) LA1780M 10 db. db. db 69 db LA178M 7.5 db 1 db 7 db 66 db LA1787M 7.5 db.5 db 8.6 db 67 db First mixer First IF amplifier Second mixer Second IF amplifier : No circuit changes from the LA178M. : Equivalent to the LA1780M circuit. (The gain is lower than that in the LA1781M and LA178M.) : The mixer circuit has been modified to improve adjacent channel suppression and interference. : Equivalent to the LA1780M circuit. No /5

25 . Changes to applications Component values that change from LA1781M/LA178M applications (Since the total AM gain has changed in the LA1787M) AM SD adjustment resistor (pin 55): Because Vsm is higher. AM level adjustment resistor (pin 1): Since the post-detection audio amplifier gain is higher than in the LA1781M and LA178M, the output level is also higher. This resistor must be changed to match the set value. AM mixer coil (pin 5), IFT coil (pin 5) damp resistor: Since the IF block gain is increased, the mixer (pin 5) and IFT (pin 5) coil damping must be adjusted. Separation adjustment resistor (pin 19): Since an internal kω resistor has been added to the pin 19 input circuit to improve the separation temperature characteristics, the value of the external resistor must be reduced from that used with the LA1780M, LA1781M, and LA178M. (See the following page.) Composite Sign 5kΩ DECODER Composite Sign 5kΩ DECODER Added kω resistor kΩ 0kΩ 0.07µF 0.07µF LA1781M/178M A160 LA1787M A160 Functions 1. Notes on the FM Front End Notes on interference rejection characteristics Intermodulation characteristics The LA1787M applies two high-band AGC functions to prevent IM (the generation of intermodulation). These are the narrow AGC (pin 58: mixer input detection type) and the wide AGC (for the pin 55 input), and this results in the antenna frequency characteristics shown in figure. The levels at which the AGC functions turn on are determined by the capacitors attached at pins 55 and f AGC Sensitivity When f = 0, 98.1 MHz AGC sensitivity dbµ The wide AGC sensitivity when pin 9 is 5 V. The narrow AGC sensitivity when pin 9 is at ground f MHz Fig. No /5

26 Notes on second-channel attenuation suppression Keyed AGC (D AGC) is a technique for achieving good characteristics for both intermodulation and secondchannel attenuation at the same time. When the desired signal is faint or nonexistent, the high-band AGC level will be essentially 0, and as a result automatic tuning may malfunction and blocking oscillation may occur in the presence of strong interfering stations. Keyed AGC helps resolve these problems. This D AGC technique uses information that has the following three frequency characteristics and is a unique Sanyo-developed system for determining the high-band AGC level. RF and ANT circuit information: Mixer input AGC Mixer circuit information: Mixer output AGC CF selectivity information: S-meter output D AGC Features Feature Only the narrow AGC sensitivity (operation at f < 1.5 MHz) is controlled by the field strength of the desired station. The narrow AGC sensitivity is controlled by a voltage (V ) that is under 0.5 V. The wide AGC can operate even when V = 0 (when the desired station is not present). The narrow and wide AGC sensitivities can be set independently. (See figure and.) The system has two AGC systems: narrow and wide AGC. (See figure 5.) Merit Effective in resolving second-channel attenuation problems. Allows effective resolution of second-channel attenuation problems without degrading three-signal characteristics. Seek operations may stop incorrectly due to the occurrence of intermodulation. It is possible to prevent the occurrence of intermodulation in the RF tuning circuit and antenna in the presence of strong interfering stations, and blocking oscillation due to AGC operation can be prevented. Settings can be optimized for the field conditions. Since the narrow AGC operates for the desired station and adjacent stations, the wide AGC sensitivity can be lowered and AGC malfunction due to local oscillator signal can be prevented. f AGC on Level (ANT input) Fig. f AGC on Level (ANT input) Fig Pin 55 capacitor: pf Narrow AGC on level dbµ keyed AGC 9 Pin 58 capacitor: 10 pf Pin 58 capacitor: 7 pf Wide AGC on level dbµ keyed AGC 9 5V Pin 55 capacitor: 10 pf f MHz f MHz Pin 59 narrow AGC and pin 55 wide AGC input levels dbµ W-AGC, N-AGC f Wide AGC on level frequency characteristics Narrow AGC on level frequency characteristics Fig.5 AGC input level frequency 10 characteristics such that V 10 RF AGC (pin ) falls under V Frequency, f MHz No /5

27 D AGC Sensitivity Characteristics AGC sensitivity Wide AGC sensitivity F 1 Second-channel attenuation improvement Desired station AGC sensitivity Narrow AGC sensitivity V (Desired station field strength) Fig. 6 A1075 D AGC Sensitivity f, V characteristics The wide AGC sensitivity is determined by the antenna and RF circuit selectivity, regardless of V. The narrow AGC sensitivity is determined by the following. The total selectivity of the antenna, RF circuit, and mixer when V 0.5 V The above selectivity and V when V < 0.5 V The improvement in the second-channel attenuation corresponds to the area occupied by the narrow AGC in the total AGC sensitivity area. Figure 8 on the next page shows the actual operation of the circuit. f AGC on Level (ANT input) The fu input level at which antenna damping turns on dbµ f MHz Fig. 7 f D = 98.1 MHz fu = 98.1 MHz f Second-channel pad ANT IN V IN A1076 No /5

28 Notes on D AGC (Keyed AGC) 55 W-AGC DET 58 N-AGC DET 90µA S-meter 1 9 ANT DUMPING VS-meter A1176 Fig. 8 The antenna damping current from the pin due to the pin diode flows when the V pin reaches the - V BE level. The narrow AGC operates as follows. When pin V9 > pin V: The narrow AGC turns off. When pin V9 < pin V: The narrow AGC turns on. No /5

29 The LA1787M includes two AGC circuits in its front end block. Antenna input limiter using a pin diode. FET second gate control The AGC input pin is pin 59, and the AGC circuit turns on when a signal of about 0 mvrms is input. AGC activation The pin diode drive circuit turns on when V is greater than or equal to about 1 V, and input limitation is applied to the antenna circuit. In application circuits, there will be an attenuation of about 0 to 0 db. Next, when an adequate current flows in the antenna attenuator pin diode, the inductance falls, the FET second gate voltage drops, the FET gm falls, and the AGC operates. The recommended FET is the Sanyo SK6, which is an enhancement-type MOSFET. Therefore, full AGC is applied when the voltage, V G-S, between the second gate and the source is 0. Note that if a depletion-type MOSFET is used, AGC will not be applied unless V G-S is less than V AGC Characteristics Fig.9 fr = 98.0 Hz = 8 V Ta = 5 C VAGC V 6 5 Range where the AGC does not operate AGC level due to the pin diode: about 5 db AGC level due to the MOSFET second gate: about 5 db ANT IN dbµ Mixer The mixer circuit in this IC is a double-balanced mixer with both balanced input and balanced output. Input circuit type Emitter input Input impedance: 5 Ω Due to optimized device geometry, emitter current, the bias, this IC achieves the following performance. Mixer input usable sensitivity: 15 dbµ Mixer input IMQS: 90.5 dbµ (For an oscillator level of 00 mvrms) * The mixer input IMQS is defined as: OSC MIX INPUT MIX OUT MIX MIX OUT MIX INPUT MIX fr = 98.8 MHz, no input fu1 = 98.8 MHz, 1 khz, 0% modulation fu = 99.6 MHz, no modulation The interference 1 and input levels such that generated intermodulation output signal-to-noise ratio becomes 0 db when an interference signal with the same level as the mixer input is input, and distortion occurs in the mixer. Mixer circuit Fig. 10 A1077 No /5

30 Oscillator Figure 11 shows the type of oscillator circuit used in this IC. It includes both an oscillator and an oscillator buffer. 18pF VT 5pF 0pF 5 AM/FM OSC BUFFER OUT A1078 Fig. 11 Figure 1 shows the type of FM first IF amplifier used in this IC. It is a differential single-stage amplifier. 0Ω TO MIX FM IF input Ω 0Ω Specifications Input impedance: 0 Ω Output impedance: 0 Ω Gain: 0 db Fig. 1 A1079 No /5

31 . FM IF Notes on the FM SD and SD adjustment The figure below presents an overview of the FM SD and the IF count buffer..9v R R Band muting HOLE CLET Muting drive output R STEREO IND S-meter IF count buffer FM IF 9 6 5V IF count output.5v 5V SD STEREO/MONO Fig. 1 A11759 Figure 1 shows the relationship between the FM SD, the IF count buffer output, the S-meter, and the muting drive output. V V 8 Larger values of R S-meter V Smaller values of R V 6 V over 0.7 V V over 0.7 V 5 V V AC V DC OFF On as an SD signal IF count buffer OFF SD ON IF counter output off SD ON Stereo Mono 0.7 V 5 V.5 V 0 V RDS and other types of SD detection can be used by switching these modes. New LA178M functionality: For stereo input (when the V6 pin voltage is 0.7 V), when this pin is shorted to ground (0.1 V or lower) the IC will operate in forced mono mode. Fig. 1 A11758 No /5

32 Transient response characteristics during automatic tuning The transient characteristics for SD and IF count buffer on/off operation are determined by the time constants of the RC circuits attached to the following pins. (1) Muting time constant: pin () S-meter time constant: pin () AFC time constant: pin There are two points that require consideration when using fast tuning. (1) The SD time constant due to the S-meter time constant Since the current I (pin ) varies with the field strength, the time constant also changes. There is no hysteresis in the comparator. If a smaller value is used for C, you must select a value for C such that the AGC does not become unstable when the pin voltage is used for keyed AGC. S-meter 10k C Fig. 15 A1080 () The SD time constant due to the pin muting voltage time constant The changes in volume due to field fluctuation during weak field reception can be made smoother by setting the attack and release times during soft muting operation. Mute drive 50kΩ Mute amp Muting time constants Attack: 10 kω C Release: 50 kω C Attack Release C Fig. 16 A11766 Antenna input such that pin 5 goes high dbµ 50 SD Sensitivity Adjustment Fig Resistance between the pin and ground kω No /5

33 However, when testing this stop sensitivity, note that when checking the waveform on the IF count buffer output (pin ), there are cases, such as that shown below, where current in the test system may be seen as flowing to ground and cause oscillation that causes the IF count buffer output to go to the output state. F.E. IF IF buffer amp 5 V 0.0 µf Test system capacitance The 10.7 MHz feeds back through ground. Fig. 18 A1081 FM Muting control pin (pin 7) (R7: 0 kω variable resistor) The db limiting sensitivity can be adjusted with R7. 15 kω FM Soft Muting (1) R7 = 7.5 kω DET out Fig.19 Output, noise db 0 kω 10 kω Noise Antenna input dbµ FM muting attenuation adjustment (pin 58) The muting attenuation can be switched between the three levels of 0, 0, and 0 db by the resistor inserted between pin 58 and ground. (Note that the exact values depend on the total tuner gain.) The noise convergence with no input is determined by the pin 58 voltage Ω R 58 R58 Mute ATT Open 0 db 00 kω 0 db 0 kω 0 db A1176 The attenuation can be set by making R smaller as listed in the table above. R Fig. 0 A11765 No /5

34 Output, noise db Output db FM Soft Muting () Fig.1 FM Soft Muting () R7 = 7.5 kω DET out 10 kω 15 kω 00 kω 0 kω Output db R7 = 7.5 kω 10 kω 15 kω Fig. DET out 0 kω Noise 0kΩ Noise Antenna input dbµ Antenna input dbµ VCC 00 kω R Quadrature detector Mute amp. (VCA) R N-AGC R Mute drive Limiter 58 1 To MIX out DET out Open 00 kω 0 kω Fig. A11767 FM muting off function Forcing this pin to the ground level turns muting off. Detector output When the pin is at the ground level, the noise convergence will be 10 db and the db limiting sensitivity will be about 0 dbµ. Antenna input Fig. A108 No /5

35 Hall detection The Hall detection function detects the level of the pin 6 quadrature input signal and then applies peak detection to that result. The result is output from pin. This circuit has three effects. (1) It assures that muting will be applied for weak inputs with an antenna input of under 5 dbµ. The amount of attenuation is referenced to an antenna input of 60 dbµ, fm = 1 khz, and a.5 khz dev output, and is variable from 10 db to 0 db when there is no input. Thus one feature of this circuit is that the weak input noise attenuation and the db limiting sensitivity for over 5 dbµ inputs can be set independently. 5 Hall Detection Output Antenna Input Characteristics Fig.5 Area muted by Hall detection V 8pin V Antenna input dbµ () When the pin 6 quadrature input is a saturated input, the pin 6 noise level (Va) is detected and a peak-hold function is applied to pin (Vb) for locations rapid field strength variations and severe multipath occurs for fields that result in an antenna input level of over 5 dbµ. 6 Va Vb 0.1µF 0 0 Fig. 6 A108 () Unique features One unique feature of the LA178M is that if there are adjacent stations such that f 1 = 98.1 MHz and f = 97.9 MHz, a search operation will not stop at 98.0 MHz. Since V AFC = 0 V and V SM =.6 V at 98.0 MHz in the situations shown in figure 7 and 8, even though Hall detection would normally not operate and SD would be high, in this IC the Hall detection circuit will operate, V Mute will be set to 1. V (over 0.7 V) and the SD signal will go low, thus preventing incorrect stopping of the search. No /5

36 Voltage between pins 7 and, V AFC V Pin 6 (SD) V Pin, V SM V Pin, V Mute V Unique Features of the LA178M Hall Detection Circuit (1) When the tuner is moved in 50 khz steps. With a 51 kω resistor between pins 7 and. With the SD sensitivity adjusted to be 0 dbµ. f 1 f Fig.7 ANT IN f = 97.9 MHz, 10 dbµ fm = 00 Hz,.5 khz dev. f 1 = 98.1 MHz, 10 dbµ fm = 1 khz,. 5kHz dev. Voltage between pins 7 and, V AFC V Pin 6 (SD) V Pin, V SM V Pin, V Mute V When the tuner is moved in 50 khz steps. With a 51 kω resistor between pins 7 and. With the SD sensitivity adjusted to be 0 dbµ Unique Features of the LA178M Hall Detection Circuit () Fig.8 f = 97.9 MHz, 0 dbµ fm = 00 Hz,.5 khz dev. f 1 = 98.1 MHz, 0 dbµ fm = 1 khz,.5 khz dev Frequency, fr MHz Frequency, fr MHz Notes on the quadrature input level When a strong field is being received the quadrature signal input (pin 6) requires a 00 mv rms input, and the detection transformer and the damping resistor between pins 6 and 7 must be designed. (We recommend the Sumida SA-08 transformer and a 10 kω resistor between pins 6 and 7.) When the pin 6 input level falls below 160 mv rms, the Hall detection circuit operates and the pin mute drive output voltage increases. Therefore, when pin 6 input is from 160 to under 00 mv rms during strong field reception, the muting circuit may or may not operate due to sample-to-sample variations between individual ICs. Furthermore, the SD function may not operate, and the audio output level may be reduced. Incorrect operation due to sample-to-sample variations and temperature characteristics can be prevented by keeping the pin 6 voltage at 00 mvrms or higher. 6 5 Pin VMute QD Input Level With pins and 7 shorted. With 5 V applied to pin. Fig.9 SA08 LA1787M IF Input Characteristics Fig.0 0. Vmute V 75 Ω 75 Ω 0.0 µf SG MHz 6 7 LA1888M QD input level dbµ THD % f khz With the resistor between 0. pins 6 and 7 open. With a 10 kω resistor between pins 6 and THD 1 khz 75 khz dev f= MHz Voltage between pins 7 and (referenced to the pin 7 voltage) No /5

37 Detector output Pin 6 AC level MPX OUT R 6-7 Vo QDIN Open 0 mvrms 5 mvrms 10 kω 80 mvrms 00 mvrms Band Muting Adjustment Procedure The muting bandwidth can be modified as shown in figure 1 with the resistor R BW between pin and 7. Bandwidth such that the pin voltage V khz R BW Muting Bandwidth 1 µf 0.7 µf 10 kω R BW SA08 Sumida ANT IN 98 MHz 100 dbµ Fig Resistor R BW between pins and 7 kω. AM AM AGC system The LA1787M RF AGC circuit takes its input from three sources: the WIDE AGC pin (pin 6), the MIDDLE AGC pin (pin 9) and NARROW AGC. There is also an IF AGC circuit. R W 1st MIX 10.7MHz CF nd MIX 50kHz CF IF Amp. DET RF st OSC X'tal 0 kω 6 Wide AGC IN Middle AGC IN Narrow AGC IN Amp. IF AGC. µf ANT damping RF AGC µf. µf Fig. A1176 No /5

38 AGC on level AM AGC f characteristics Wide AGC Operates for wide band interference Middle AGC Operates for interference within ±70 khz of the received frequency Fig. Wide AGC Operates for wide band interference Middle AGC Operates for interference within ±70 khz of the received frequency. 70 Narrow AGC Operates at the received frequency Frequency Hz Antenna damping on input level dbµ Wide Band AGC Circuit 0 Ω 0.0 µf 6dB SG 50 Ω 50 Ω ANTD 0.0 µf µf 510 Ω Fig. Received frequency: 1 MHz Pin 6 input MHz The wide band AGC circuit in this IC has the frequency characteristics shown above. The pin 6 input frequency characteristics are identical to those of the RF amplifier gate. This AGC circuit serves to prevent distortion at the FET input when a strong signal is applied to the antenna circuit. The level at which the AGC circuit turns on can be adjusted to an arbitrary level with the wide band AGC adjustment resistor. A delayed AGC on level can be handled by reducing the value of the adjustment resistor. Wide band AGC adjustment resistor 0.0 µf 0 Ω 60 Ω 1MH 100 µh 100 µh 0MH 0.0 µf FC kω 7 µf 15 pf 15 pf 57 Fig. 5 6 A108 No /5